First page of Seq ADC datasheet says:
Note Only GPIOs can be connected to the channel inputs. The actual maximum number of input channels depends on the number of routable analog GPIOs available on a specific PSoC part and package.
Set the clock frequency a bit higher than 1 MHz, ADC will display 1000.020 kHz
For the ADC I ran into the same problem (see replies http://www.cypress.com/forum/psoc-creator-software/creator-error-signal-ah0degw-expected-connect-only-one-gpio-analog-pin). I had to go with ADC SAR+AMux instead of the Sequencing SAR, as I didn't like the external connection between "internal" OPAMP and sequencing SAR.
Yes, that's what I'm doing too. But still the question remains. Why does one allow for internal connections and the other doesn't? I can guess, like maybe they didn't see the point of it- if you have more than 4 inputs that you want buffered, this has to be done externally anyway. So they didn't bother to include this design feature. That's a guess...
ok- I just read your link. That answers my question. Thanks a lot.